Wireless transmission technology is a known technology for transmitting signals or energy between electrical devices not directly connected by lines.
The electronic circuit element known as a digital isolator is one example of a wireless transmission apparatus which uses wireless transmission technology (for example, see Patent Literature (PTL) 1). The technology disclosed in PTL 1 can isolate the ground for logic signals from the ground for RF signals, and as such, is widely applicable.
This kind of wireless transmission apparatus is used as a gate driving element for, for example, an insulated gate bipolar transistor (IGBT), which is a power electronics semiconductor switching device. With this kind of power semiconductor switching device, due to fluctuation in source potential with reference to high voltage, it is necessary to insulate the DC component between within the gate driving element and the power semiconductor switching device.
Moreover, electromagnetic resonant couplers (also known as electromagnetic field resonant couplers) which employ the coupling of two electrical line resonators are one example of wireless transmission technology that has gained attention in recent years (for example, see Non-Patent Literature (NPTL) 1). These electromagnetic resonant couplers are characterized by an ability to efficiently transmit signals across a great distance.
Among these electromagnetic resonant couplers, although the structure is simplistic, an open ring type electromagnetic resonant coupler can be realized that is compact and capable of accomplishing wireless transmission in a small space (for example, see PTL 2).